Oven construction



April 2, 1969 e. B. GERRISH 3,439,906

OVEN CONSTRUCTIO N Filed Dec. 26, 1967 April 2, 1969 GB. GERRISH 3,439,906

OVEN CONSTRUCTION Filed Dec. 26, 196'? Sheet 3 of 4 United States Patent Office 3,439,906 Patented Apr. 22, 1969 3,439,906 OVEN CONSTRUCTION Grenville Bradbury Gerrish, 26 Standish Road, Melrose, Mass. 02176 Continuation-impart of application Ser. No. 422,899,

Jan. 4, 1965. This application Dec. 26, 1967, Ser.

Int. Cl. F27b 9/24; F27d 7/00 US. Cl. 2638 12 Claims ABSTRACT OF THE DISCLOSURE- An oven construction such as an open-ended housing with a conveyor disposed therein for transporting products therethrough to be heated by heating means, typically gas burners, arranged below, or above and below the conveyor. The gaseous products formed during combustion and released by the products are exhausted through ducting by an exhaust fan or the like. The volumetric capacity of the fan is sufficient to exhaust the maximum volume of gaseous products. When the gaseous products happen to be less than the volumetric capacity of the fan, air entering the housing through passageways located below the lowermost heating means makes up the difference.

This is a continuation-in-part application of my copending patent application Ser. No. 422,899, filed Jan. 4, 1965, and now abandoned.

This invention relates to an oven construction arranged to heat conveyed products at substantially atmospheric pressure, and particularly to such an oven construction whereby means are provided to ensure that such substantially atmospheric pressure is maintained during heating.

The new results and advantages of this invention will become apparent as the following description of certain embodiments thereof and methods of practicing the same proceeds.

In the accompanying drawings I have shown certain embodiments of this invention and have illustrated certain methods of practicing the same in which:

FIGURE 1 is a plan view of an oven of this invention showing one embodiment thereof and broken away to indicate extent;

FIGURE 2 is an elevational view of the oven of FIG- URE 1;

FIGURE 3 is a view taken along FIGURE 1;

FIGURE 4 is a view taken along FIGURE 3;

FIGURE 5 is a plan view of an oven of this invention showing another embodiment thereof and broken away to indicate extent;

FIGURE 6 is an elevational view of the oven of FIG- URE 5;

FIGURE 7 is a fragmentary cross-section taken along the line 7-7 of FIGURE 5;

FIGURE 8 is a fragmentary cross-section taken along the line 8-8 of FIGURE 6;

FIGURE 9 is a fragmentary cross-section taken along the line 99 of FIGURE 6;

FIGURE 10 is a fragmentary cross-section taken along the line 1010 of FIGURE 6;

FIGURE 11 is a longitudinal sectional view of one section of the oven shown in FIGURE 5;

FIGURE 12 is a cross-sectional view taken along the line 1212 of FIGURE 11;

FIGURE 13 is an elevational view of an oven of this invention showing the preferred embodiment thereof and broken away to indicate extent; and

the line 3-3 of the line 4-4 of FIGURE 14 is a cross-sectional view taken along the line 14-14 of FIGURE 13.

Referring now to the drawings, FIGURES 1-4 show a sectional griddle oven of a well-known construction embodying the present invention. The elongated oven is made up of a series of individual sections; an advance group of which have conventional hoods and the trailing group of which have no hoods. Each section has a bottom wall 22 and side walls 24 forming an elongated combustion chamber. Supported by the side walls 24 are a series of longitudinally spaced shafts 28 carrying spaced rollers 30 for supporting an endless band 32 which forms the oven griddle. The endless band 32 has as a product transporting traverse extending between the entrance and exit openings of the oven, and a return traverse 34 below the bottom wall 22 of the combustion chamber. A series of longitudinally spaced rollers 36 mounted on cross shafts 38 supported by side walls 24, support return traverse 34.

As shown in FIGURE 4, transversely inwardly extending sealing means 40 are fixed to an intermediate point of side walls 24. Sealing means 40 extends longitudinally of side walls 24 and include wear strips 41 bearing downwardly on the edge portions of endless band 32 to form a running seal between the product transporting traverse and the combustion chamber 26.

Heating means in the form of gas burners 42 extend transversely of the combustion chamber 26 at longitudinally spaced intervals, being integral with pipes extending inwardly through one side wall 24 of the chamber. Four burners 42 are illustrated in each section. The burners 42 operate with an atmospheric gas pressure system, of any well-known type, wherein air is mixed with the combustible gas in a venturi-type aspirator with the air being fed under pressure to aspirate the gas fuel into the burner pipes.

Extending longitudinally beneath the bottoms of the collective combustion chambers is an exhaust duct which at longitudinally spaced intervals communicates through openings 51 Whose areas can be regulated by dampers 52. A plenum 54 is provided in each chamber section and is superimposed above the openings 51. The top wall 56 of each plenum 54 is supplied with ports 57 for the ingress of products of combustion emanating from the burners. Dampers 52 are controlled by hand rods 58 extending transversely outwardly of the oven.

The internal oven exhaust duct 50 is connected by ducting 59 to suitably externally mounted exhaust fan 60 which can be set to operate at any desired volumetric capacity within a known range. The exhaust fan 60 is preferably operated at a constant volumetric capacity. The hooded section of the oven may be provided with any desired conventional mode of ventilation above the product transporting traverse of endless band 32.

Air inlet openings 62 are provided in side walls 24 of each combustion section. The openings 62 are located above the top wall 56 of plenum 54 and below the burners 42. As shown, each section is provided with two pairs of opposed openings 62. The size of the openings 62 are determined on the basis of the exhaust fan 60 setting which is made to be at least equal to the volume of gaseous products of combustion formed at the desired maximum setting of burners 42. The setting of fan 60 is made together with the setting of dampers 52. Openings 62 are suitably sized to provide make-up air when the burners 42 are operated at less than the maximum setting. The sizing of openings 62 should be sufficient to provide air in an amount to make up the difference between the volumetric setting of fan 60 and the volume of gaseous products of combustion formed during the minimum setting of burners 42. Thus, substantially atmospheric pressure will be maintained within the combustion chambers 26 at all operating conditions between the minimum and maximum setting of burners 42.

So long as the rate of production of products of combustion at the gas burners 42 creates a volume of gas above or equal to the volumetric operating capacity of fan 60 then air will not pass through openings 62 into chambers 26. However, when the burners 60 are set so that the gaseous products of combustion are less than the fan 60 operating volumetric capacity, the fan 60 will draw make-up air through the openings 62. As a consequence, the zones of chambers 26 above openings 62 will be maintained at substantially atmospheric pressure, thereby preventing leakage of air through seals 40.

Calculations demonstrate that in a typical thirty-eight burner griddle oven composed of five tandem aligned eight-foot sections and delivering 36,000 B.t.u.s per burner per hour at maximum fire and 8,000 B.t.u.s

per burner per hour at minimum fire, the rate of production of the total products of combustion may vary from 595 c.f.m. at 800 F. at high fire to 132 c.f.m. at 800 F. at low fire. When a fan 60 is provided which has a capacity of 1047 c.f.m. at 800 F., the make-up deficiency pulled through the openings 62 at an assumed ambient temperature of 70 F. will run from a rate of 190 c.f.m. at maximum fire to 384 c.f.m. at minimum fire. When heated to 800 F., these volumes become 452 c.f.m. and 915 c.f.m., respectively, thus satisfying the fan demand. If there are twenty openings 62, each two inches in diameter, providing a total inlet area of 20 times .0218 square foot or 0.436 square foot, the maximum velocity through the openings will be 384/ .436 or 880 feet/minute. At 70 F., the pressure differential required to produce a velocity of 880 f.p.m. through the openings 62 is approximately 0.06 inch of water, a pressure which is negligible in its effect on the operation of the burners. Thus, with such a fan 60 and opening 62 arrangement as hereinabove described, the combustion chamber 26 remains at substantially atmospheric pressure regardless of the rate of production of the products of combustion.

Operation of the fan at constant volume in excess of the volume of the gaseous products of combustion improves stability of temperature control and aids in securing uniform distribution of exhaust throughout the entire length of the oven. If the ports 57 through the top Walls 56 of the plenums 54 are made /1. inch in diameter and each eight-foot section has fifty-four ports 57, the total inlet area for each section will be 0.172 square foot and can satisfy one-fifth of the 1047 c.f.m. capacity of the fan at 209 c.f.m. per section. The velocity through each port 57 will therefore be 1220 f.p.m., which is desirable to insure even distribution of flow.

Another embodiment of the oven construction of the present invention is illustrated in FIGURES -12 as a tunnel oven having burners both above and below the product transporting traverse of the conveyor. In this embodiment, an endless metal sheet or woven wire belt conveyor 70 has a return traverse 104 and a product transporting traverse disposed substantially centrally through a sectionalized tunnel 72 whose walls form a combustion chamber 74. Rollers 76 supported on longitudinally spaced shaft 78 support the conveyor 70 during its travel through the tunnel.

Upper burners 80 are shown as being equally longitudinally spaced, and lower burners 82 being equally longitudinally spaced and lying in planes disposed vertically equidistant between successive pairs of upper burners 80. As in the case of the griddle oven of FIGURES 1-4, air at a variable controlled pressure is supplied through a pipe header 83 and combustible gas at atmospheric pressure is fed through a pipe header 84 to aspirators 86-, one for each burner. Valve 87 is a motor operated air valve for controlling the primary air pressure.

Longitudinally spaced opposed openings 88 are provided in the side walls of the tunnel and extend from the inner surface thereof to opposed passageways 89 disposed intermediate the inner and outer surfaces of the side walls. Passageways 89 extend downwardly to horizontal ducts 90 and 91 extending from each side inwardly toward a central longitudinally extending exhaust duct 92. Similar openings 93, one for each section, are shown at the bottom of the oven chamber for use where certain portions of the oven require predominantly bottom heat on the product. Openings 93 also have ducts 94 leading to exhaust duct 92. Exhaust duct 92 is sectionalized into zones, each section of duct 92 communicating with an outlet conduit 95 leading to an exhaust fan 96 and a discharge section 97. Each fan 96 is set to operate at a constant volumetric capacity following the same criterion as for setting the fan 60 of the griddle oven of FIGURES 14. That is, fan 96 is set to operate at a volumetric capacity equal to or exceeding the rate of production of products of combustion emanating from all the burners at maximum fire setting. It is desirable to set fan 96 to have a volumetric capacity exceeding the maximum rate of production of gaseous products of combustion by the rate of production of gases released by the products being treated. Suitable dampers arranged in openings 88 and 93 can be adjusted to vary the areas thereof for accommodating the requirements of any particular loads.

Opposed air inlet passageways 98 and 99 are provided through the side walls of the oven and are longitudinally spaced therealong. The passageways 98 and 99 are disposed below the lower burner 82 and above exhaust duct 92. As in the case of openings 62 of the embodiment of FIGURES 14, passageways 98 and 99 are suitably located and suitably sized to provide make-up air at a rate to supply any deficiency in the volume of gases necessary to satisfy the constant volumetric capacities of fans 96 over and above the rate of production of combusted products. Two pairs of passageways 98 and 99 are provided in each section.

It should be understood that the calculations given as an example for the griddle oven of FIGURES 1-4 apply in principle to the tunnel oven of FIGURES 5-12 although the operating temperatures, B.t.u. input requirement range and exhaust fan volume may vary. For example, in a tunnel oven baking a product giving up large quantities of moisture, the exhaust fan volume required to remove this moisture may exceed that required to remove only the products of combustion.

FIGURES 13 and 14 illustrate the preferred embodiment of the oven construction of the present invention. This oven is similar to that of FIGURES 5-12, having an elongated insulated housing with product entrance and exit openings 112 and 114, respectively, at opposite ends thereof. The housing 110 is sectionalized in a manner similar to the ovens of the two previously described embodiments. Each section is provided with longitudinally spaced, transversely extending upper and lower burners 116 and 118, respectively, disposed in heat exchange relationship above and below the product transporting traverse 120 of an endless band conveyor 122. The product transporting traverse 120 is suitably supported by a plurality of longitudinally spaced rollers 124 extending between the walls of housing 110. The return traverse 126 of conveyor 122 is suitably supported below housing 110 by longitudinally spaced transversely extending rollers 128 supported by support legs 130 fixed to the exterior of housing 110.

A longitudinally extending exhaust duct is disposed in an upper section of housing 110, and is separated into two compartments 141 and 142, respectively, by a channel member 143. Each compartment 141 and 142 is provided with a plurality of longitudinally spaced openings 146 communicating between the interior thereof and the interior of housing 110. Another longitudinally extending duct 150 is disposed above housing 110 and receives the exhausted gaseous products from the compartments through upwardly extending longitudinally spaced hollow damper boxes 152 communicating with each compart;

ment. An upwardly extending duct 160 centrally disposed on and communicating with duct 150 is fixed to the suction side of an exhaust fan 170.

A plurality of longitudinally spaced openings 180 is provided through the side walls of housing 110 below the lower burners 118 and above the bottom wall of housing 110. As in the case of the openings 98 and 99 of the previously described embodiments, openings 180 are suitably sized and spaced to provide sufiicient make-up air at a rate for supplying any deficiency in the volume of gases necessary to satisfy the constant volume capacity setting of the fans 170 over and above the rate of production of combusted products and the gases released by the products being treated. Similarly, the volumetric capacity of fan 170 is set in the same manner as that of the previously described embodiment. Likewise, the calculations given as an example for the oven of FIGURES 1-4 apply in principle to this preferred embodiment.

The plumbing for the gas burners 116 and 118 is essentially the same as that for the burners 80 and 82 of the oven of FIGURES 5-12 and need not be described again.

The expression substantially atmospheric pressure has been used throughout this description as regards to the pressure conditions within the described ovens of the present invention during all operating conditions between maximum and minimum burner settings. It should be understood that, as used herein, substantially atmospheric pressure defines a pressure within the ovens which is slightly below atmospheric pressure as that term is commonly understood. The calculations given as an example for the griddle oven of FIGURES l-4 clearly show a pressure differential of .06 inch of water existing across the openings in the walls of the oven. It is apparent that the pressure differential is necessary for atmospheric air to enter through the openings into the oven. It will additionally be recognized by those skilled in the art that the substantially atmospheric pressure within the oven will vary slightly as gauged along the longitudinal length thereof for the oven openings to atmosphere are spaced rather than continuous and as such a slight pressure variance in the oven between the openings will exist.

I claim:

1. An oven construction comprising: an elongated tunnel having insulated side wall portions and an insulated bottom portion; an elongated driven conveyor having a product transporting traverse extending longitudinally of and forming the top portion of said tunnel; sealing means between the side edges of said product transporting traverse and said side wall portions of said tunnel; gas producing burner means disposed between said product transporting traverse and said bottom portion of said housing in spaced heat exchange relationship with said product transporting traverse; elongated partition means disposed in said tunnel intermediate said top and bottom portion to define together with at least one of said portions of said tunnel, an exhaust duct having at least one opening below said burner means; suction fluid exhaust means operatively communicating with said exhaust duct for exhausting outwardly of said tunnel substantially all of the gases formed during any operation of said burner means; and at least one of said side wall portions having passageway means therethrough intermediate said burner means and said one opening of said exhaust duct of a size to permit ingress of atmospheric air into said tunnel in an amount such that essentially uniform pressure will be maintained in said tunnel during any operation of said exhaust means.

2. An oven construction as set forth in claim 1 wherein said burner means extend transversely with respect to said product transporting traverse and are longitudinally spaced in said tunnel, at least one of said side wall portions has a plurality of passageways therethrough spaced longitudinally therealong.

3. An oven construction as set forth in claim 1 wherein said burner means extend transversely with respect to said product transporting traverse and are longitudinally spaced in said tunnel; said partition means is disposed in said tunnel below said burner means to define with said bottom portion said exhaust duct; both of said side wall portions have a plurality of passageways therethrough spaced longitudinally therealong.

4. An oven construction comprising: an elongated tunnel having insulated side wall portions and insulated top and bottom portions; an elongated driven conveyor having a product transporting traverse extending longitudinal ly through said tunnel intermediate said top and bottom portions; a plurality of upper and lower gas burner means disposed at least above and below said product transporb ing traverse in spaced heat exchange relationship with said product transporting traverse; elongated partition means disposed in said tunnel to define with at least one of said side wall portions and at least part of said bottom portion an exhaust duct having at least one opening above said upper burner means and at least one opening below said lower burner means; suction fluid exhaust means operatively communicating with said exhaust duct for exhausting outwardly of said tunnel at least all of the combustion gases formed during any operation of said burner means; and at least one of said side wall portions having passageway means therethrough disposed intermediate said burner means and said one opening of said exhaust duct below said burner means of a size to permit ingress of atmospheric air into the said housing in an amount such that essentially uniform pressure will be maintained in said housing during any operation of said exhaust means.

5. An oven construction as set forth in claim 4 wherein said burner means extend transversely with respect to said product transporting traverse and are longitudinally spaced in said tunnel; at least one of said side wall portions has a plurality of passageways therethrough spaced longitudinally therealong.

6. An oven construction comprising: an elongated hollow insulated housing having product entrance and exit openings at opposite ends thereof; a conveyor having a product transporting traverse located within said housing and extending at least between said entrance and exit openings; gaseous product producing heating means spaced longitudinally of said housing and located at least below said product transporting traverse to heat product being conveyed on said transporting traverse; duct means having ingress means communicating with the interior of said housing and a discharge portion located to discharge gaseous medium from said housing externally of said housing; gaseous fluid moving means cooperable with said duct means for discharging gaseous fluid from said housing through said discharge portion, said fluid moving means having a volumetric capacity no less than the rate of production of the combined gaseous products of combustion and the gases released by the product being heated; and passageway means spaced longitudinally of said housing in open communication between the exterior and interior of such housing at a level below the level of the lowermost of said heating means and below said product transporting traverse.

7. An oven construction as set forth in claim 6 wherein said passageway means are of such a size to permit ingress of atmospheric air into said housing at a rate to maintain essentially uniform pressure in said housing during any operation of said fluid moving means.

8. An oven construction as set forth in claim 6 wherein said heating means is disposed below and above said product transporting traverse.

9. An oven construction as set forth in claim 6 wherein said heating means is a plurality of longitudinally spaced transversely extending variable combustion rate gas burners disposed above and below said product trans porting traverse; said fluid moving means is a suction fan means operable to discharge at least said combined gaseous products at the maximum combustion rate of said gas burners and the gases released by the product being heated; said passageway means are a plurality of longitudinally spaced openings sized to collectively permit ingress of atmospheric air into said housing at a rate to maintain essentially uniform pressure within said housing.

10. A method of heating articles in an oven comprising: conveying a plurality of articles to be heated in a given path extending through an elongated oven, heating said articles during said conveying by gaseous product producing heating means spaced longitudinally along and laterally adjacent said path, exhausting gaseous medium from within said oven at a given rate at least equal to the maximum rate of production of gaseous product by said heating means, and admitting air from outside said oven into said oven at locations spaced along said path and at a level lower than said path and said heating means at a rate to maintain said given rate when the gaseous product production by said heating means is less than said maxi mum rate to maintain essentially uniform pressure within said oven during said heating.

11. A method of heating articles as set forth in claim 10 wherein said heating causes said articles to release gaseous products, said exhausting is at another given rate at least equal to the maximum rate of production of gaseous product of said heating means and said articles, and said admitting is at rate to maintain said another given rate.

12. A method of heating as set forth in claim 10 whereing said admitting is at a velocity such that the operation of the burners is not materially affected.

References Cited UNITED STATES PATENTS 11/1929 Mulholland 2634l 11/1965 Fannon 263-8 

